Cooling System Description

COOLING SYSTEM





The Saturn cooling system uses a pressured coolant surge tank and doesn't have a reservoir or overflow bottle. All components of the cooling system are filled from the surge tank and no additional bleeding is necessary.
At cold start-up, the thermostat will be in the closed position. The engine water pump will pump coolant through the cylinder head and block as well as the throttle body. Coolant is also pumped through the heater inlet hose to the heater water pump. The heater water pump assists the engine water pump by increasing the coolant flow rate through the heater core. Coolant returns from the heater core through the heater outlet hose to the engine block. Any air in the engine block or heater core is carried by coolant to the surge tank through the head degas hose. Coolant then flows from the surge tank back to the engine block through the return hose.
When the coolant returns to the engine block, it flows over the thermostat element. When the coolant temperature reaches 90 degrees C (194 degrees F), the thermostat will begin to open. The coolant will flow through the upper radiator hose, through the radiator, and back to the engine through the lower radiator hose. Any air in the radiator is carried by coolant to the surge tank through the radiator degas hose.
If the coolant temperature exceeds 105 degrees C (221 degrees F) at engine shutdown, the heater water pump will be enabled for several minutes. The heater water pump will pump coolant in a loop through the engine and to the radiator while the cooling fans run to reduce the coolant temperature.